[openwrt/openwrt] dropbear: increase default receive window size

[LEDE Commits]

blocktrron pushed a commit to openwrt/openwrt.git, branch openwrt-23.05:
https://git.openwrt.org/5cc1918a7a0bed42eaf8a26afff6091336c62af5

commit 5cc1918a7a0bed42eaf8a26afff6091336c62af5
Author: David Bauer <mail at david-bauer.net>
AuthorDate: Thu Dec 28 23:16:02 2023 +0100

    dropbear: increase default receive window size
    
    Increasing the receive window size improves throughout on higher-latency
    links such as WAN connections. The current default of 24KB caps out at
    around 500 KB/s.
    
    Increasing the receive buffer to 256KB increases the throughput to at
    least 11 MB/s.
    
    Signed-off-by: David Bauer <mail at david-bauer.net>
    (cherry picked from commit f95eecfb21ff08662e022accd30e8254028ff63b)
---
 package/network/services/dropbear/files/dropbear.init | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/package/network/services/dropbear/files/dropbear.init b/package/network/services/dropbear/files/dropbear.init
index b82e967cbc..a40b5f7bae 100755
--- a/package/network/services/dropbear/files/dropbear.init
+++ b/package/network/services/dropbear/files/dropbear.init
@@ -155,6 +155,12 @@ dropbear_instance()
 	PIDCOUNT="$(( ${PIDCOUNT} + 1))"
 	local pid_file="/var/run/${NAME}.${PIDCOUNT}.pid"
 
+	# Increase default receive window size to increase
+	# throughput on high latency links
+	if [ "${RecvWindowSize}" -eq "0" ]; then
+		RecvWindowSize="262144"
+	fi
+
 	procd_open_instance
 	procd_set_param command "$PROG" -F -P "$pid_file"
 	[ "${PasswordAuth}" -eq 0 ] && procd_append_param command -s